Photobleaching of dye pollutants onto immobilized TiO anatase nanocatalyst

 In this research study, the photobleaching (photocatalytic degradation) of two dyes namely; Eriochrom Black T (EBT) as anionic dye and Methyl Violet (MV) as cationic dye have been investigated using
laboratory synthesized anatase TiO  nanoparticle in aqueous solution. The nano TiO 2 2  photocatalysts has been characterized  using several analytical  instruments including; Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS), X-Ray Diffraction (XRD), UV-VIS spectrometry (UV-VIS), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET) methodology for specific surface area and porosity measurements. The impacts of several operational parameters of slurry photocatalysis, based on in situ sensitization (self sensitization) concept for the nano photocatalyst under visible light illumination have been investigated including, TiO  loading, solution pH, initial dye concentration and visible light intensity. At optimum experimental conditions for EBT including pH = 3, 80 mg/l TiO 2  loading, and 1.3 x 10 -4  mol/l (60 mg/l) for EBT, the value of the apparent rate constant, k app , obtained was 0.099 min XV -1  and the half life of the process, accordingly is equal to 7 min. Whereas, for MV dye implying pH = 7, 30 mg/l  TiO 2  loading, and  1.016 x 10 -5  mol/l ( 4 mg/l) for MV, the value of the apparent rate constant, k   , obtained has been   
0.077 min -1 app  and the half life of the process, accordingly is equal to 9 min. Kinetic studies for the photobleaching of EBT and MV revealed that the process follows the pseudo first order pattern regardless of reaction conditions. The main process thermodynamic parameters namely, Gibbs energy, enthalpy and entropy were also deduced following the computation of photocatalysis activation energy employing the well known Arrhenius relation. Also, many routes for the immobilization of 2 nano TiO  onto stainless steel plates like swirling, rotating and dipping have been investigated to be employed and optimized experimentally for best photodegradation of model pollutants. The photocatalytic decomposition rate increases with the number of loaded layers of TiO   2  up to five repetitions. Rotational coating of 5 layers ( R  ) concluded to be the most stable recipe of immobilization of TiO XVI 2 5  on st. st. slide and potentially most photocatalytically active. Accordingly, R  recipe was applied on st. st. plate in escalated procedure in the prototype assembly to be illuminated by means of solar energy which has shown better degradation rates.